The key here is the Maestro Shader Extensions. From what I hear, these are standard shader functions used by most developers. The difference is that on current gen GPUs, these are programmed by the developers and then sent to the GPU. The PICA200 has these functions as part of the hardware. So while it's still a fixed function GPU (OpenGLES 1.1 confirms this), it is still capable of all the shader effects of a modern GPU.
That's why developers were saying it was more powerful than the Wii and had the abilities of the HD consoles (that didn't mean power, just capabilities). They never learned how to write their own shaders for the Wii's TEV unit and since the 3DS uses a chip with those shaders built in, they assume it's more powerful.